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Showing 4 results for Convergent-Divergent Nozzle
Ali Akbar Moltani Shahrakht, Mohammad Javad Maghrebi,
Volume 15, Issue 7 (9-2015)
Abstract
The prediction of distillation zone is very important in steam turbine blades and steam nozzles. In identification of distillery with equilibrium method, as the steam flow contacts the two-phase dome, the second phase formes and flow properties will pass the distillery without any jumping, therefor after crossing the saturation curve, the droplet formation transpires, but in non-equilibrium method by a sudden increase in pressure, called “condensation shock” a discontinuity in the flow characteristics is seen and after crossing the saturation curve, the formation of droplets starts. In this paper, numerical analysis of a vapor-liquid two-phase transonic flow in a convergent-divergent nozzle with and without shock is investigated. Effects of stagnation temperature at nozzle inlet, viscosity and geometry is studied using thermodynamic equilibrium and non-equilibrium methods and results compared with experimental datas. Roe numerical method is used for vapor-liquid two-phase flow numerical solution. The main properties of the flow at the boundary of elements is extrapolated by MUSCL third order acuracy and time discretization is performed using Lax-Wendroff explicit two-step method of second order accuracy. It is observed that the results of non-equilibrium solution, has more correspondence to experimental results and Condensation starts earlier in the nozzle with further expansion rate. By increasing the temperature at nozzle inlet, the place at which condensation starts goes forward. Also in comparision with non-viscous flow, the shock location in viscous flow comes closed to the throat.
M.r. Babaeyan , M. Hojaji,
Volume 19, Issue 7 (7-2019)
Abstract
In this study, the effect of the use of dual protuberances as a thrust vector control method in a supersonic convergent-divergent nozzle with a Mach number of 2 is experimentally investigated. The nozzle total pressure in all experiments is considered constant. Air is the working fluid in these experiments. The used protuberances are two cylindrical elements that are placed in front of the flow in the divergent part of the nozzle. These protuberances are installed at 60% and 90% of the length of the nozzle divergent portion from the nozzle throat and are simultaneously applied in the main flow path. The protuberances are installed in opposite walls. Effect of changing the penetration ratio of the protuberances [H/D] on the thrust vector angle and the components of the thrust vector is obtained by measuring the forces acting on the nozzle. Also, the flow field was measured by a Schlieren system, as well as, the pressure variations on the nozzle walls were measured. The results show that the use of dual protuberances can have a significant effect on the angle of the thrust vector and increase the angle of the thrust vector up to 4.35 degrees in the implemented conditions of this study. Also, the results reveal that this method can reduce the axial component of thrust up to 5.5% in the worst case of implemented conditions.
M.m. Fakhari, H.r. Bokaei, B. Shahriari,
Volume 20, Issue 2 (1-2020)
Abstract
In this paper, the effect of nozzle divergent section geometry on fluid flow and heat transfer within the convergent-divergent nozzle numerically and experimentally is investigated. Axisymmetric supersonic flow simulation for the converging-diverging nozzle is conducted. The flow field is a steady turbulent two-dimensional flow. The working fluid is a combustion product and is considered as a compressible ideal gas. The flow field is simulated using the commercial code FLUENT. The equations are discretized implicitly with the second order of accuracy. In this study, two convergent-divergent nozzles have been analyzed that the divergent part of one is a cone-shaped and the other is bell-shaped. The calculated parameters in the simulation have been compared with the experimental results. Based on the simulation results and the values obtained in the experimental test, the error is less than 4% that is acceptable and appropriate. According to the results, flow simulation accuracy is appropriate.
A. Sharafi, D. Mokhtari,
Volume 20, Issue 5 (5-2020)
Abstract
In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.
